African National Congress (ANC) secretary-general Ace Magashule says claims made by former president Jacob Zuma that former minister Ngoako Ramatlhodi was a spy should not be ignored.

On Monday, Zuma, who appeared for the first time before the judicial commission of inquiry into State capture, named Ramatlhodi as a spy "who was recruited in Lesotho".

Zuma also referred to Ramatlhodi's own comments to the commission in November last year, when he accused Zuma of having "auctioned" the country to the Gupta family.

Ramatlhodi has since denied the allegations, challenging Zuma to a lie detector test.

Magashule, who came to listen to Zuma's testimony on Tuesday, told reporters on the sidelines: "They (spy claims) are serious. We can't just ignore them, and some of us, unlike what the young boy wrote in the book (referring to journalist Pieter-Louis Myburgh), we have been around.

He said he had been a National Executive Committee (NEC) member under the leadership of former presidents Nelson Mandela, Thabo Mbeki, Zuma and now Cyril Ramaphosa, "...so, I know some of the things which president Zuma might be actually saying".

"Jacob Zuma was chief of intelligence of the ANC, he will even know better things that we don't know and when you are a leader of that organisation, you become loyal to that organisation."

Magashule said the former president came to the ANC head office last week Friday, "informing the [party] that he might say certain things which may not sit well with the ANC".

He said there have been suggestions from party members to establish their own commission to discuss what Zuma has claimed.

"I am sure we will discuss [it] as the ANC," he said.